206308691861 has 2 divisors, whose sum is σ = 206308691862. Its totient is φ = 206308691860.

The previous prime is 206308691839. The next prime is 206308691893. The reversal of 206308691861 is 168196803602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202247178961 + 4061512900 = 449719^2 + 63730^2 .

It is a cyclic number.

It is not a de Polignac number, because 206308691861 - 2¹⁴ = 206308675477 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206308694861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103154345930 + 103154345931.

It is an arithmetic number, because the mean of its divisors is an integer number (103154345931).

Almost surely, 2^206308691861 is an apocalyptic number.

It is an amenable number.

206308691861 is a deficient number, since it is larger than the sum of its proper divisors (1).

206308691861 is an equidigital number, since it uses as much as digits as its factorization.

206308691861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 746496, while the sum is 50.

The spelling of 206308691861 in words is "two hundred six billion, three hundred eight million, six hundred ninety-one thousand, eight hundred sixty-one".